Today's need for smaller and more fuel efficient automobiles stimulates automobile manufacturers and their competitors to produce faster and lighter engines and transmissions. This translates into a need for better lubrication of critical high speed rotating components in both engines and transmissions.
To accomplish this, product engineers are designing transmission components with many new small and deep hole lubrication circuits to provide oil to delicate high speed bearings. Faced with the challenge of making these holes, manufacturing engineers have been called upon to reinvent deep hole drilling, especially for small holes, which are typically one and a half millimeters or less in diameter and five to ten times that in depth.
Conventional twist drilling of such holes, although not difficult in low volume applications, has traditionally been avoided for high volume production applications because of the limited drill life of small diameter drills. Twist drilling deep, small diameter holes has been impractical and inefficient for typical high volume automotive production applications.
Against this background, the need has arisen to investigate alternative small hole-making process technologies, such as those required to drill crankshaft lube holes in engines under development at high production volumes.
The three most common hole drilling technologies are twist drilling, gun drilling and electrical discharge machining (EDM). Conventional twist drilling of small diameter holes has traditionally been avoided in a high volume environment because of limited drill life. Conventional electrical discharge machining does provide a small hole-making alternative to drilling, but the process is generally too slow for high volume production applications. Accordingly, the need has arisen for a technique to increase cutting speed by an order of magnitude, thereby providing a potentially viable alternative to conventional drilling techniques.
In an effort to compare the different drilling technologies, comparative data has been collected. Information has been gathered from manufacturing operations using a transmission output shaft as a typical example of a high volume part with a variety of holes requiring numerous drilling operations. This part has both shallow and deep holes produced conventionally with both twist and gun drilling operations. It also has a small, 1.2 millimeter diameter hole, which currently is twist drilled. Two additional 1.0 millimeter diameter lube holes were added to this part for a high load truck application.
Until the present work, there remained an unfulfilled requirement providing a cost-effective alternative to conventional drilling.
As an example of unfulfilled need, product engineers have wished to add small lubrication holes to power train components to reduce friction and improve the durability of engines and transmissions. Manufacturing engineers, on the other hand, have not, until the present invention, had a cost effective, robust process available with which to produce such small holes.